Electric circuit breaker



July 5, 19 E. B. WEDMORE ELECTRIC CIRCUIT BREAKER 3 Sheets-Sheet 1 Filed llqrch 30 1925 m1 an. 9% A w 1% F 0 v Y .p lv 1 5 1 w T V 4 .1 1, Z i v 4 Inventor;

J y 1932- E. a. WEDMORE 1,866,495

ELECTRIC CIRCUIT BREAKER Filed March 30. 1925 3 Sheets-Sheet 2 i I co o0 l 1.5% 33: i 534 '1 I ii .L D L 1 L J INVENTOR July 5, 1932. WEDMORE 1,866,495

ELECTRIC CIRCUIT BREAKER Filed llarch 30, 1925 3 Sheets-Sheet 3 A I I I I I .1 I z 1 :45 z z 4c? 4 7 I 1 Awe/147m fiqmvzrr/flwzepu 5-42 A III], [III 1111 11 I I I I I I I I I 1 1 I I! I the breaker during the rupture 0 Patented July 5, 1932 UNITED STATES PATENT OFFICE RDIUND BASIL WEDIOBE, OF LONDON, ENGLAND, ASSIGNOR TO THE BRITISH ELIO- TRICAL AND ALLIED INDUSTRIES RESEARCH ASSOCIATION, OF LONDON, NGLAND,

A BRITISH ASSOCIATION mc'rmc cracnrr 33mm Application fled larch 80, 1986, Serial Io. 19,820, and Great Britain April 5, 1984.

This invention consists in improvements in or relating to electric circuit-breakers and has for its object to improve the effect of paella instruments under all conditions of over- Generally s eaking in such circuit-breakers contact is roken under oil or other fluid and hitherto it has been thought to be of advantage to utilize magnetic effects produced in the circuit in accelerating the rupture. In fact the modern tendency is, by various constructional features, to increase the magnetic effect or actually to produce a relatively strong magnetic field in the region of the separating contacts.

Under normal conditions the are which is produced when the contacts are separated under oil or the like has (i. e. when the arc is short) a comparatively low resistance and this resistance increases until ultimately the circuit is broken. Particularly under extreme conditions, for example short-circuit conditions, an enforced increase in the resistance of the are, as will occur if it is lengthened by the presence of the magnetic field, while the current value is still maintained abnormal- 1 high, will in fact, result in an increased llberation of energy within the circuit-breaker. This inmany cases results in danger to life and damage to the circuit-breaker itself.

The present invention is designed to eliminate this drawback and may be stated broadly to consist in so proportioning the effective magnetic field in relation to the speed with which the contacts are separatedthat rupture of the circuit is obtained with, as nearly as possible, minimum liberation of energy in the circuit-breaker even under short-circuit conditions.

If the contacts are separated relatively slowly the presence of magnetic effects may comprise the equivalent of increasing the speed of separation so that the effective speed with which the circuit is broken, or in other words. the effective speed with which the length of the arc is increased may be such as to reduce the energy liberated in the circuit-breaker. It is now found, as indicated above, that if the speed is increased too much while the current value is high the arc energy is increased insteadof decreased. There is therefore an optimum value for what we may term the efiective speed of operation of any particular circuit-breaker in dealing with any estimated amount of energy. The effective s eed must be understood to include not only t e speed of separation of the 'contacts but the modification of that speed which is brought about by the presence of a magnetic field. Consequently also there is an optimum value of the magnetic field or effect. As the magnetic effect tends to increase proportionateiy with the square of the current it is obvious that very powerful effects may be obtained even on a small circuit-breaker under short-circuit conditions.

Generally speaking, therefore, I have now found that instead of the usual tendency to increase the'magnetic effects in a circuitbreaker, it is of advantage to decrease these effects to such an extent that under unusually abnormal conditions, such as short-circuit conditions, the effective speed of operation of the circuit-breaker is controlled to give the most advantageous results, that is to say, to liberate as nearly as possible, the minimum energy in the circuit-breaker. The present invention may, therefore, be said to comprise in an electric circuit-breaker which would otherwise have an appreciable magnetic field associated with the are produced during the rupture of the circuit, means for reducing the said magnetic field substantially as and for the purpose above described.

It is not practicable to estimate with great precision the maximum short-circuit current a given circuit-breaker may have to deal with and even if the device were perfectly adjusted for this particular value, it might on emergency, or due to unforeseen conditions, be called upon to deal with a larger amount of energy and owing to the way in which the magnetic effects increase a serious loss of rupturing capacity may readily follow just when it is most desirable that the circuitbreaker should operate at its best. i

I find it is preferable, therefore, to de nd upon speed rather than on magnetic e ects for the rupturing of the circuit.

According to another aspect 'of the invention an electric circuit-breaker having means to determine the resultant magnetic force acting upon the are produced at the contacts of the circuit-breaker is characterized in that said means is such that the resultant magnetic force is less than it would be if no such means were provided, for the purpose of enabling, as above stated, the circuit to be ruptured with as nearly as possible a minimum liberation of energy in the circuit-breaker. Preferably, said means is so designed, having regard to the speed of separation of the contacts of the circuit-breaker, that the time interval during which an arc is maintalned at the contacts is such that the energy released by said are is or approaches a mummum.

According to one feature of the invention in a circuit-breaker of the type in which one or more arcs tend to be deflected by proxim ity of other current-carrying conductors or by the proximity of magnetic materlal there is provided a mass of magnetic material so arranged that its attractive effect upon the arc reduces or overcomes the attractive effect of said current-carrying conductors or said first-mentioned magnetic material. Alternatively, there may be provided auxiliary current-carrying conductors, preferably connected in series in the circuit to be broken by said circuit-breaker, arranged so that the forces upon said are due to said auxiliary conductors tend to oppose those set up due to the aforesaid current-carrying conductorsor said first mentioned magnetic material.

For the better understanding of this invention four preferred arrangements of a circuit-breaker will now be described with reference to the accompanying drawings, in which Figures 1 and 2 represent diagrammatically double-break circuit-breakers employing auxiliary current-carrying conductors for the purpose of this invention;

Figures 3 and 4 represent diagrammati cally double-break circuit-breakers employing masses of magnetic material for the purpose of this invention, and

Figure 5 illustrates one construction of double-break circuit-breaker showing the parts drawn to scale in correct relative position, and Figures 6, 7 and 8 illustrate modified constructions to a smaller scale embodying the arrangements shown in Figures 2, 3 and 4 respectively.

Like reference numerals indicate like parts wherever applicable in each of the several figures of the drawings.

In each of the figures of the drawings, 10, 10 indicates a conductor which is to be interrupted by the circuit-breaker at two places 15 and 16. It is assumed that in each case the circuit-breaker is enclosed in an iron tank tracted to the iron in a. direction outwards from the centre of each fi e.

In the example shown in Figure 1, a consistin of four conductors 11, 12, 13, 14 1s connecte in series with the conductor 10 and is disposed in the circuit-breaker tank between the breaks 15, 16, whereat the arc occurs. The loop is arranged so that the current in the conductor 11, which is adjacent to the are 15,

is in the same direction as that through the are 15,- and similarly the current in the conductor 13 is in the same direction as that in the are 16 which is adjacent to the conductor 13. Thus it will be seen that therewill be forces tending to attract the arcs 15 and 16 towards the conductors 11 and 13, res tively. The dimensions of a circuit-brea er are so designed that this force is equal to, or is as nearly equal to as is practicable, the force due to the 110I1 tank and other causes such as current-car 'ng conductors acting upon the arc. Thus it will be seen that the resultant force acting on the arc will be small or zero.

The conductor 12 is arranged parallel and adjacent to the moving contact-bar 17 of the circuit-breaker and carries a current in the same direction as the current in the moving contact-bar and thus tends to attract the lat ter. The purpose of this arrangement is to prevent undue acceleration of the contactbar 17 by magnetic forces due to the other conductors or to the tank of the circuit-breaker or due to both.

In Figure 2, the loop 11, 12, 13, 14 is made integral with and connected in series with the contact-bar 17 so that, when the circuit-breaker opens, the loop 11, 12, 13, 14 travels with the contact-bar 17 It will be seen that except for this difference the arrangement shown in Figure 2 is similar to that in Figure 1. It will be appreciated, however, that there is no provision in Figure 2 for the prev zantion of the acceleration of the contact-bar 1 In the arrangement shown in Fi ure 3, a mass of magnetic material takes tile place of the conductors 11, 12, 13, 14 in Figures 1 and 2. A plate of iron 20 is supported upon an insulator 21 from the frame or casing of the circuit-breaker so that it lies close to the lit contact 15. A similar plate of iron 22 is supported on an insulator 23 close to the contacts 16. A third plate of iron 24 is arranged parallel to the contact-bar 17. Although these plates may be separately formed they are preferably as one piece, as shown in Figure 3. The faces of the pieces of iron 20 and 22 may, if desired, be protected by a la er of insulating material. It will be seen t at if the iron casing of a circuit-breaker is close against the are 15 or 16 it will tend to attract the arc; the pieces of iron 20 and 22 are dimensioned and adjusted so as to tend to neutralize this and other magnetic forces acting upon the arc. The piece of iron 24 is arranged parallel to the contact-bar 17 so that it tends to attract the bar 17 thereby to preforces upon t vent undue acceleration of this part due to other stray magnetic forces.

In Figure 4 the mass of iron is itself carried u on the contact-bar. Two iron plates 20 an 22 are supported by insulators 21 and 23 upon thecontact-bar 17 so that they are means of reventin or minimizing the magnetic acce eration 0 the contact-bar 17 In Fi re 5, a construction ofcircuitbreaker is illustrated in'detail. The main lead conductor 10 passes through an insulator to the conductors 11, 12 and 13, whereof the conductors 11 and 13 are preferably each encased in an insulating sleeve, as illustrated.

The conductor 13 passes through another insulator 31 and is electrically connected by a conductor indicated diagrammatically at 14,

which is in the plane of the insulator tops,-

and passes through an insulator 32 to the main contacts 15 of usual or well-known construction. The contacts 15 are provided with auxiliary or spark contacts 33 as well understood; and on the other side of the break, main contacts 16 are shown with their auxiliary or spark contacts 34. The crossbar 17' is mechanically connected to the movable ones of the contacts 15 and 16,- and the fixed contact 16 is electrically connected throu h an insulator 35 to the other main lead 10. shield 46 of insulating material is provided between the insulators 31 and 35 to prevent an accidental bridging of the contacts carried y these insulators.

The conductor 12 is formed with a collar 36 which fits loosely over an insulated switchauxiliary contacts, the conductors 11, 12 and. 13, and cross-bar 17 are enclosed in the usual oil-containing tank 44, preferably provided in the usual manner wlth a lining 42 enclosed by the cover 40. The normal oil level is indicated at 43 and the position of the center-line of the cross-bar 17, when'the switch is, fully open, is indicated at 45.

A constructor of a circuit-breaker accord ing to this invention will be able, by wellknown methods, to calculate the electromagnetic forces which, without the presence scription is given b of the conductors 11, 12 and 13, would arise in the circuit-breaker. Equally, also, by well-known methods, he can calculate the necessary positions of the conductors 11, 12 and 13 in relation to the other parts of the circuit-breaker to obtain the uired .neutralizin efi'ect so as to'leave the spring 41 as substantially the sole means to control the speed of separation of the electrodes. Figures 6, 7 and 8 are sim'lar to Figure 5 but embody the diagrams shown respectively inFigures 2, 3 and 4. Thus in Figure 6'the conductors 13 and 11 are carried by insulators 47 on the cross-bar. The moving contacts are' mounted on insulators 48 on the cross-bar and are connected tothe conductors 13 and 11 by means of the conductors 17 and- 12. v

' In Figures 7 and 8 the arrangements are substantially as described in connection with Figures 3 and 4,- a mass of ma etic material 20, 22, 24 bein mounted on xed insulators 21 and 23 in igure 7, while in Figure 8 magnetic masses 20, 22 are mounted on the cross-bar 17 through insulators-21, 23. 7

It is evident that although in the above description it has been stated that the conductors 11, 1 2, 13, 14 and the pieces of iron 20 and 22 a'redesigned and disposed so as to minimize the magnetic forces acting upon the arcs, it is not essential that this should be the case, for the design may be such that the forces actin on the arcs may be reduced to 'anv require extent.

It will be appreciated that the above deway of exam 1e only and that many mo ifications may e made without departing from the scope of'this invention.

I claim:

1. An electric circuit breaker in which there .is a single series circuit havin ductors and a breaking oint, a con uctor portion adjacent such point, and a further conductor portion adjacent a part of the circuit that moves in the breaking o eration of the breaker, said conductor portlons being so arranged that the current flowing in them at any instant produces electromagnetic effects tending res ectively to prevent deflection of the arc ormed at the breaking point and to prevent undue acceleration of the said moving part brought about by interaction between said moving part and adjacent parts of the breaker caused by the electromagnetic efi'ects set up by the current flowing in the said moving part.

2. An electric circuit breaker comprising a air of contacts, a contact bar normally brldging such contacts and movable ina direction substantially perpendicular to its length in the breaking of the circuit, a current-carrying conductor disposed adjacent said bar and arranged so that electromagnetic forces due to the current flowing therein exert an effect upon said bar tending to conoppose other electromagnetic forces present in the breaker which would otherwise accelerate unduly the speed of the circult breaking movement of said bar.

. 3. An electric circuit breaker comprising a current-car 'ng conductor arranged in series in the circuit to be broken, a p a1r of contacts, a contact bar normally bugging such contacts and movable in the bre ng of the circuit in a direction substantially perpendicular to its length and away from said conductor, said conductor being so arranged in relation to said bar that, at any instant, current flowing in the same direction in both these parts sets up electromagnetic forces which tend to oppose other electromagnetic forces resent in the breaker which-would otherwise accelerate unduly the speed of the circuit breakin movement of said bar.

4. A circuit reaker'having a pair of cooperating contacts which are bridged by an arc on breaking circuit, which are will be urged away from the shortest path between the contacts by electromagnetic forces due to adjacent parts of the breaker, and means to produce other electromagnetic forces opposing the aforesaid forces to retain the arc substantially in the shortest path between the contacts.

5. A circuit breaker having a air of cooperating contacts which are bri ged by an arc on breaking circuit, which are will be urged away from the shortestipath between the contacts by electromagnetic forces due to adjacent parts of the breaker, and a conductor carrying current and situated so as to produce other electromagnetic forces opposm the aforesaid forces to retain the arc su stantially in the shortest path between the contacts. q

6. A circuit breaker having a air of cooperating contacts which are bri ged by an are on breaking circuit, which are will be urged away from the shortest path between the contacts by electromagnetic forces due to adjacent parts of the breaker and a conductor connected in series with the contacts and situated so as to produce other electromagnetic forces opposing the aforesaid forces to retain the are substantially in the shortest path between the contacts. 7. A circuit breaker having a pair of co operating contacts which are bridged by an are on breaking circuit, which are will be urged away from the shortest path between the contacts by electromagnetic forces due to adjacent parts of the breaker and a body of magnetic material situated so as to produce other electromagnetic forces opposing the aforesaid forces to retain the arc substantially in the shortest path between the contacts.

8. A circuit breaker having two fixed and two moving contacts in series whereof the conducting leads to the fixed contacts exaccuse tend substantially parallel to one another, whereby an are formed between the coo erating contacts will be urged away from e shortest path between the contacts by electromagnetic forces and a conductor carrying a current and situated betweenthe irs of contacts so as to have a portion substantially parallel to the line joining ea pair of separating contacts with the current flowing in the same direction, so as to produce other electromagnetic forces opposing the aforesaid forces tocontrol the position of the arc.

9. A circuit breaker having two fixed and two moving contacts in series whereofthe conducting leads to the fixed contacts extend substantially parallel to one another whereby an are formed between the cooperating contacts will be urged away from the shortest path between the contacts by electromagnetic forces and conductors connected in series with the contacts so as to have a portion lying substantially parallel to the line joining each pair of separating contacts with the current flowing in the same direction, so as to produce other electromagnetic forces opposing the aforesaid forces to control the position of the are.

10. A circuit breaker having two fixed and two moving contacts whereof the conducting leads to the fixed contacts extend substantially parallel to one another whereby an are formed between the cooperating contacts will be urged away from the shortest path between the contacts by electromagnetic forces and a body of magnetic material situated between the pairs of contacts so as to produce other electromagnetic forces opposing the aforesaid forces to control the position of the arc.

11. A circuit breaker having a fixed contact and a moving contact, a moving conductor associated with the moving contact and situated so that when a current flows in it electromagnetic forcesdue to other parts of the breaker act on it tending to accelerate or retard its movement, and means for producing other electromagnetic forces opposing the aforesaid forces so that the rate of movement of said conductor is substantial- 1y independent of the current flowing in it.

12. A circuit breaker having a fixed contact and a moving contact which are bridged by an are on breaking circuit which are will be urged away from the shortest path between the contacts by electromagnetic forces due to adjacent parts of the breaker, a moving conductor associated with the moving contact and situated so that when a current flows in it electromagnetic forces due to other parts of the breaker act on it tending to accelerate or retard its movement and means for producing other electromagnetic forces opposin the aforesaid forces so that the rate of e ongation .of the arc depends substantially'only on the operating mechanism and is substantially independent of the current flowing in the arc.

13. A circuit breaker having two fixed and two moving contacts, a moving conductor connected between the moving contacts so as to move in a direction substantially perpendicular to its length, conducting leads extending from the fixed contacts substantially parallel to one another in the direction in which the moving contacts move to make circuit, and means to produce electromagnetic forces tending to retard the opening movement of the moving contacts.

14. A circuit breaker having two fixed and two moving contacts, a moving conductor connected between the moving contacts so as to move in a direction substantially perpendicular to its length, conducting leads extending from the fixed contacts substantially parallel to one another in the direction in which the moving contacts move to make circuit, and a fixed conductor connected in series with thecontacts and situated parallel with the moving conductor so that the currents in the two conductors are in the same direction and so that the moving conductor recedes from the fixed conductor on breaking circuit.

15. A circuit breaker having two fixed and two moving contacts, a moving conductor connected between the moving contacts so as to move in a direction substantially perpendicular to its length, conducting leads extending from the fixed contactssubstantially parallel to one another in the direction in which the moving contacts move to make circuit, and a body of magnetic material situated adjacent to the moving conductor so that the latter recedes from it on breaking circuit.

16. A circuit breaker having two fixed and two moving contacts, a moving conductor connected between the moving contacts so as to-emove ina direction substantially perpendicular to the line joining said contacts, conducting leads extending from the fixed conconductor is formed with a 100 tacts substantially arallel to one another in the direction in w ich the moving contacts move to make circuit, wherein the moving I havin one side situated between the con ucting eads to the fixedcontacts in which side the current travels in a direction opposite to that in which it would travel if the conductor were straight.

17. A circuit breaker having) a (pair of cooperating contacts which are ri ged by an 18. A circuit breaker having two fixed and two moving contacts in series whereof the conducting leads to the fixed contacts extend substantially parallel to one another, an enclosing case of magnetic material having a wall situated adjacent a point of separation of said contacts whereby an are formed between the cooperating contacts will be urged away from the shortest path between the contacts by electromagnetic forces and means for producing other electromagnetic forces opposing the aforesaid forces so as to control the position of the arc.

19. A circuit breaker having a fixed contact and a moving contact, a moving conductor associated with the moving contact, an enclosing case of magnetic material having a wall situated adjacent said moving conductor so that the latter approaches and recedes from it so that when a current flows in said conductor electromagnetic forces act on it tending to accelerate or retard itsmovement and means for producing other electromagnetic forces opposing the aforesaid forces so that the rate of movement of said conductor is substantially independent of the current flowing in it. v

20. A circuit breaker having two fixed and two moving contacts, a moving conductor connected between the moving contacts so as to move in a direction substantially perpendicular to its length, a case of magnetic material having a wall situated adjacent said moving conductor so that the latter approaches and recedes from it in operation and means to produce electromagnetic forces tending to urge said moving conductor away from said magnetic wall.

In testimon whereof I aflix my si aturei ED BASIL WEDM RE.

are on breaking circuit, a container of. mag-. Q netic material having a wall adJacent the arc whereby magnetic forces are set up urging the are away from the shortest path between the contacts, and means to produce other electromagnetic forces opposing the aforesaid forces to'retain the are substantially in the shortest path between the contacts. 

